Definition of oil yellow
1
often capitalized O&Y
a
: any of several oil-soluble yellow dyes
b
or
oil yellow II
: a carcinogenic azo dye C6H5N2C6H4N(CH3)2 formerly used in coloring butter and oils; para-dimethyl-aminoazobenzene — called also
butter yellow, methyl yellow
2
: a moderate greenish yellow that is greener and duller than citron yellow and deeper than linden green
